Elasticsearch's extensive REST API is a fundamental feature that allows users to integrate, manage, and query indexed data in diverse ways, with numerous examples of its application across various industries. The article provides an overview of essential API categories such as Document, Search, Indices, cat, and Cluster APIs, each serving distinct purposes like handling documents, querying data, managing indices, formatting data outputs, and managing clusters. While this guide highlights key API calls and offers practical cURL command examples, it is not exhaustive, and advanced users might benefit from an accompanying cheat sheet on Elasticsearch Cluster API best practices. The REST API's versatility is a significant factor in the popularity of Elasticsearch and the ELK stack, and the article encourages experimentation to gain proficiency. Additionally, it notes that APIs may evolve over time, necessitating awareness of updates and deprecations to maintain effective usage. For users of the managed ELK solution Logz.io, a public API based on the Elasticsearch Search API is available, albeit with some limitations, allowing for search queries and alert management.